Effect of CT number to relative electron density curves acquired at different tube voltage and current on radiotherapy dose calculation

Chand, Bhagat; Priyamvda,; Kumar, Mukesh; Prasher, Sangeeta; Kumar, Mukesh

doi:10.1088/1742-6596/2267/1/012140

Cited by 2 publications

(1 citation statement)

References 17 publications

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“…The mean HU information of each insert on the central slice is noted and is related to the respective electron density value. [ 7 ] There are multiple phantoms available from various vendors that can be used to carry out this task, some of them include PTW Electron density phantom,[ 8 ] Pro-RT ED phantom,[ 9 ] Sun Nuclear Advanced Electron Density (AED) Phantom,[ 10 ] and Gammex RMI 467 tissue characterization phantom. [ 11 ] Conventionally, the CT-ED curve is produced based on the average Hounsfield values determined on the central slice of the electron density phantom.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Computed Tomography Numbers on Multiple Imaging Systems using Single and Multislice Methods

Ramachandran

Mehta

Arrington

et al. 2023

Journal of Medical Physics

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Aim: The aim of this study is to determine the variation in Hounsfield values with single and multi-slice methods using in-house software on fan-beam computed tomography (FCT), linear accelerator (linac) cone-beam computed tomography (CBCT), and Icon-CBCT datasets acquired using Gammex and advanced electron density (AED) phantoms. Materials and Methods: The AED phantom was scanned on a Toshiba computed tomography (CT) scanner, five linac-based CBCT X-ray volumetric imaging systems, and Leksell Gamma Knife Icon. The variation between single and multi-slice methods was assessed by comparing scans acquired using Gammex and AED phantoms. The variation in Hounsfield units (HUs) between seven different clinical protocols was assessed using the AED phantom. A CIRS Model 605 Radiosurgery Head Phantom (TED) phantom was scanned on all three imaging systems to assess the target dosimetric changes due to HU variation. An in-house software was developed in MATLAB to assess the HU statistics and the trend along the longitudinal axis. Results: The FCT dataset showed a minimal variation (central slice ± 3 HU) in HU values along the long axis. A similar trend was also observed between the studied clinical protocols acquired on FCT. Variation among multiple linac CBCTs was insignificant. In the case of the water insert, a maximum HU variation of −7.23 ± 68.67 was observed for Linac 1 towards the inferior end of the phantom. All five linacs appeared to have a similar trend in terms of HU variation from the proximal to the distal end of the phantom, with a few outliers for Linac 5. Among three imaging modalities, the maximum variation was observed in gamma knife CBCTs, whereas FCT showed no appreciable deviation from the central value. In terms of dosimetric comparison, the mean dose in CT and Linac CBCT scans differed by <0.5 Gy, whereas at least a 1 Gy difference was observed between CT and gamma knife CBCT. Conclusion: This study shows a minimal variation with FCT between single, volume-based, and multislice methods, and hence the current approach of determining the CT-electron density curve based on a single-slice method would be sufficient for producing a HU calibrations curve for treatment planning. However, CBCTs acquired on linac, and in particular, gamma knife systems, show noticeable variations along the long axis, which is likely to affect the dose calculations performed on CBCTs. It is highly recommended to assess the Hounsfield values on multiple slices before using the HU curve for dose calculations.

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Section: Introductionmentioning

confidence: 99%

Investigation of Computed Tomography Numbers on Multiple Imaging Systems using Single and Multislice Methods

Ramachandran

Mehta

Arrington

et al. 2023

Journal of Medical Physics

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An Approach for Automation of CT Number Linearity Measurement on the TOS Phantom Image

Mira Anjani,

Choirul Anam*,

Heri Sutanto

et al. 2024

IJSRST

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Assessment of the computed tomography (CT) number linearity is an important part in the Quality Control (QC) procedures of CT images. An automated method is needed for simplify the measurement process of this parameter. This study aims to develop an automated method for measuring CT number linearity on the TOS phantom images scanned with Toshiba Aquilion Lightning CT scanner with variations of tube current, tube voltage, and slice thickness. The automation began with segmenting the phantom object with a threshold of - 200 Hounsfield units (HU). Then, the centroid was determined for the phantom mask. The air object inside the phantom and its centroid were segmented utilizing a threshold of - 900 HU. By performing a simple rotation operation between the two obtained centroids (i.e., phantom and air centroids), the central coordinates of Delrin, acrylic, nylon, and polypropylene materials were determined. CT number linearity and its coefficient of determination (R2) were calculated. The proposed method was evaluated with datasets scanned from variations of tube current, tube voltage, and slice thickness. The automated CT number linearity measurements were successfully developed. The CT number linearity showed acceptable results for all variations (R2>0.99). Moreover, no significant changes in CT numbers of all materials compared to the standard values were noticed.

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Effect of CT number to relative electron density curves acquired at different tube voltage and current on radiotherapy dose calculation

Cited by 2 publications

References 17 publications

Investigation of Computed Tomography Numbers on Multiple Imaging Systems using Single and Multislice Methods

Investigation of Computed Tomography Numbers on Multiple Imaging Systems using Single and Multislice Methods

An Approach for Automation of CT Number Linearity Measurement on the TOS Phantom Image

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